Abstract: A method of the production of a plastic lens substrate is provided which comprises the steps of retaining a starting plastic block material on a processing material retainer, holding a processing tool on a tool holder, the processing tool having a processing end portion dimensioned to be smaller than the dimension of the block material, manipulating the processing tool and/or the block material to thereby subject both of the same to relative movement, and repeating the steps mentioned upon exchange of the processing tool for one for use in subsequent processing. The method leads, in automated manner with improved production efficiency and increased cost saving, to a plastic lens substrate having a lens surface such as a spherical surface, a toric surface, an aspherical surface, a progressive surface, a combination of aspherical and toric surfaces or a combination of progressive and toric surfaces. Also disclosed is an apparatus for producing the lens substrate.

Abstract: An oxygen sensor comprises a solid electrolyte having one surface covered with a porous metallic film and the other surface on which a sinter of a metal and an oxide of the metal is disposed. Electromotive force (EMF) is developed between the film and the sinter during its use.